PowerPoint
GSM TCH Call Drop & Solutions:: : 32-36pt:
:: : 24pt: To master definitions of call drop indicators and
relevant countersTo master causes of the three types of call drop
and the corresponding solutionsTo know analysis of call drop and
location of call drop problem with traffic statisticsTraining
goals> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Indicator definitionCall drop due to radio link faultCall
drop due to handover failureCall drop due to LAPD link
failureHandling of call drop problemContents> G91, B170G137,
B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.TCH call
drop rate(incl. HO)=Number of TCH call drops*100%/Number of TCH
seizures(including handover)Indicator definition> G91, B170G137,
B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Hardware
failureTransmission problemParameter settingIntra-network and
inter-network interferenceCoverage problemAntenna system
problemImbalance between uplink and downlinkFactors that affect the
TCH call drop rate> G91, B170G137, B207G174, B239G171, B189:: :
30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Parameter setting:Radio link timeoutRxlev_access_minMin DL
power on HO candidateMAIOFactors that affect the TCH call drop
rate> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Indicator definitionCall drop due to radio link faultCall
drop due to handover failureCall drop due to LAPD link
failureHandling of call drop problem
Contents> G91, B170G137, B207G174, B239G171, B189:: :
30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to radio link failure
> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Causes
for call drop due to radio link failure & handlingCall drop due
to radio link failureMain causes1.Weak coverage, poor radio
signal2.Interference3.Unreasonable setting of radio
parameter4.Handover failure5.Equipment hardware fault6.Antenna
system fault7.Subscribers behaviorHandling procedures1.Check radio
parameters. Adjust unreasonable setting s of radio
parameters2.Check indicators like RQ and level of idle interference
band, reduce or eliminate radio interference3.Check if coverage
problem exists through DT4.Check and eliminate equipment
fault5.Check antenna system> G91, B170G137, B207G174, B239G171,
B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Indicator definitionCall drop due to radio link faultCall
drop due to handover failureCall drop due to LAPD link
failureHandling of call drop problem
Contents> G91, B170G137, B207G174, B239G171, B189:: :
30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to handover failurePrinciple: After MS receive Handover
command or assignment (corresponding handover control timer is
started by BSC) from the original cell , MS hasnt accessed into the
target cell, nor has it returned to the original cell. Which means
MS failed to occupy TCH in target cell and send handover complete
or assignment complete, but also failed to return to TCH in
original cell and send Handover failure or assignment failure, thus
it is disconnected with network. At the same time, the
BSC-controlled handover control timer expires, and MSC will be
notified to clear channel, and it will count this abnormal call as
call drop due to handover failure.Classification of handover
control timer in BSC:T3107 expires(intra-cell handover)T3103
expires(inter-cell handover under one BSC)T8 expires(inter-BSC
handover)> G91, B170G137, B207G174, B239G171, B189:: :
30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to intra-cell handover failureCall drop due to handover
failure
> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to inter-cell handover failure
> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to inter-BSC handover failure
> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Main
causes for call drop due to handover failure & handling
proceduresCall drop due to handover failureMain causesHandling
proceduresInterferenceHardware faultUnreasonable setting of radio
parametersCongestion in adjacent cellInappropriate adjacent cell
relation or wrong adjacent cell dataUnreasonable setting of
handover parameters, which results in Ping-Pong handoverCheck radio
parameters, adjust the unreasonable setting, and add necessary
neighbor relationsCheck indicators like RQ and level of idle
interference band, reduce or eliminate radio interferenceCheck
equipment hardware, change panels with problems> G91, B170G137,
B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Indicator definitionCall drop due to radio link faultCall
drop due to handover failureCall drop due to LAPD link
failureHandling of call drop problem
Contents> G91, B170G137, B207G174, B239G171, B189:: :
30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Call
drop due to LAPD link failurePrinciple: When LAPD link breaks,
calls on carriers will be interrupted. BSC counts after it receives
message showing that LAPD link is broken.Main causes for call drop
due to LAPD link failure & handling procedures:Call drop due to
LAPD link failureMain causesHandling proceduresBTS hardware
faultBTS transmission problemBSC hardware faultInvestigate &
eliminate BTS hardware faultInvestigate & eliminate BTS
transmission problemInvestigate & eliminate BSC hardware
fault> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights
reserved.Indicator definitionCall drop due to radio link faultCall
drop due to handover failureCall drop due to LAPD link
failureHandling of call drop problemContents> G91, B170G137,
B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Flow of
handling call drops
> G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Locate
& analyze call drop with traffic statisticsLocate cell with
high call drop rateConfirm call drop typeConfirm call drop on
carrierAnalyze causeProblem solvedPerformance report of BSC
levelPerformance report of cell levelPerformance report of cell
level CS basic measurementWarning statisticsTRX measurementCell
radio measurementAnalysis of common problemAnalysis of specific
problemWarning analysisAnalysis of traffic statisticsSignaling
analysisOther network optimization methodsFrom macro to micro
viewConvenient for problem location and analysisCount call drops on
carrierFrom common to specificExecution & problem solution>
G91, B170G137, B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved.Locate
& analyze call drop with traffic statisticsCommon causes for
call dropsResult in call dropUnreasonable setting of handover
parametersUL/DL unbalanceUnreasonable setting of other
parametersCoverage problemEquipment hardware
faultInterferenceCommon problem is analyzed> G91, B170G137,
B207G174, B239G171, B189:: : 30-32pt:
(1-5):: : 28-12pt: ZTE Corporation. All rights reserved. ZTE
Corporation. All rights reserved.Thanks!BTS
BSC
Measure Report
MSC
Measure Result
Connection failure
Ms
Clear Request(Radio Interface Failure)
A1
BSC
BTS:TRX
MS
ASSIGNMENT COMMAND
CHANNEL ACTIVATE
A2
CHANNEL ACTIVATE ACK
SET T3107
T3107 Timeout
A1
BSC
Old BTS:
MS
HANDOVER COMMAND
CHANNEL ACT
A2
CHANNEL ACT ACK
SET T3103
New BTS
HANDOVER COMMAND
T3103 Timeout
A1
BSC
Old BTS:
MS
HANDOVER COMMAND
CHANNEL ACT
A2
CHANNEL ACT ACK
SET T8
New BTS
HANDOVER COMMAND
T8 Timeout
A cell suffers from high TCH call drop rate
Call drop of handover failure
Call drop of LAPD
Analysis of call drop types
Call drop of RF loss
If radio parameters set reasonably?
If interference exists?
An equipment hardware fault?
Any fault with BTS transmission?
Any equipment hardware fault?
Any hardware fault at BTS?
Eliminate hardware fault
Any antenna system fault?
Eliminate transmission fault
Any coverage problem?
Improve coverage
Any hardware fault at BSC?
Eliminate hardware fault
Eliminate antenna fault
Complete Eliminate equipment fault
If radio parameters set reasonably?
If interference exists?
Check& eliminate interference
Adjust radio parametersNo
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
